A new Hierarchical Agent Protocol Notation

Agent interaction descriptions (or protocols) are a key aspect of the design of multi-agent systems. However, in the authors' extensive experience, the notations commonly used for specification are both difficult to use, and lack expressiveness in certain areas. Some desired modular representations are impossible to express, while others result in specifications that are unwieldy and difficult to follow. In this paper we present a new notation for expressing interaction protocols, focussing on key issues that we have found to be problematic: the ability to define flexible data-driven protocols; representation of roles including their mapping to agents; and hierarchical modularity. We provide the semantics for our notation and illustrate its use with three diverse case studies. Finally we evaluate this notation using objectively assessable criteria that we argue contribute substantially to pragmatic usability, and using a human subject evaluation of the notation's usability.